ES2349625T3 - COLD ISTATIC COMPRESSION METHOD. - Google Patents

Abstract

A cold isostatic compression method comprising: covering a mandrel (36) of an isostatic compression mold (2) with a first material; assembling an isostatic compression mold (2) by coaxially placing said mandrel within a cylindrical pressure support element (30) and sealing said cylindrical pressure support element at opposite ends, one of said opposite ends of said support element being cylindrical pressure sealed with a spaced end plug (34) of said mandrel; compressing said first material isostatically within said isostatic pressure mold to produce a first layer (38) in a form of a tube closed at one end and opened at the other end thereof; disassemble said isostatic pressure mold to allow said first layer to be covered with a second material; covering said first layer with said second material; reassemble said isostatic pressure mold; compressing said second material isostatically to form a compacted second layer (40) and to stratify the first and second layers; disassemble the mold and disassemble the tubular structure.

Description

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Cold isostatic compression method.

Field of the Invention

The present invention relates to a method of cold isostatic compression in which material is compacted inside the isostatic compression mold. More particularly, the The present invention relates to a method in which two or more layers of material are formed within an isostatic compression mold and the second of the layers is isostatically compressed against the first of the two layers to compact the second layer.

Background of the invention

Cold isostatic compression is a technique well known that is used to form filters, elements Structural and ceramic membranes. In isostatic compression cold, a granular form of a material to be compacted is placed inside an elastic isostatic compression mold that is Sometimes called a bag. The granular material can be a ceramic or metallic powder or a mixture of powders, binder and plasticizing agents The isostatic compression mold is then positioned inside a pressure vessel and subjected slowly at a hydrostatic pressure with hot or cold water to compact the granular material in an untreated form that subsequently it is suitable, it can be fired and sintered.

The isostatic compression mold has a cylindrical configuration to produce cylindrical articles. A example of a process that applies to the formation of bars of Tungsten is described in US Pat. No. 5,631,029. In this patent, tungsten fine powder is isostatically compressed inside a tungsten ingot.

GB 2,342,102 A describes a procedure of compression to manufacture reinforced ceramic composite materials with fibers, where the fibers are mixed with a binder for form a porous compression material that is introduced inside of a pressure tool with a layer of compression material and a core The material and the core are compressed to form a untreated body

GB 2 165 483 A refers to a method for set up a compressed tubular body that has a notch in the outer surface of it. The body is configured by compressing isostatically particulate material in a mold elastic.

US 4,604,252 describes a procedure for Production of a hollow or solid profile of dry powder material which is executed by means of a flexible way. Flexible form it is placed under an external pressure on its total length to compact the powder In order to produce endless profiles, it is carried out An extrusion procedure.

An important application for materials Ceramics refers to the manufacture of membrane elements ceramic Such ceramic membrane elements are manufactured from a ceramic that is selected to conduct ions of any of oxygen or hydrogen at high temperatures. In a membrane Selective oxygen, the heated membrane is exposed to a gas that It contains oxygen that is ionized on a cathode side of the membrane. Under a driving force of a partial pressure of oxygen differential, oxygen ions are transported through the membrane to an opposite anode surface. Oxygen ions are combine on the anode side of the membrane to leave electrons that are transported through the membrane or a separate electronic path to ionize oxygen on the side of membrane cathode.

A recent development in the technology of ceramic membranes consists of forming a thin dense layer of material on a porous support. The dense layer conducts ions and the Support structure works like a porous filtration network to add structural support to the dense layer. Porous support it can also be manufactured from a material that is the same capable of transporting ions so that it is active in the oxygen separation

Ceramic membranes such as those that have described above, they can be in the form of plates or tubes It is difficult, however, to impart a complex architecture in such membranes. In the manufacture of tubular structures composed, the tube is formed by a procedure such as molding or extrusion of sliding and sintering. After what which, a dense layer can be deposited by spraying on The outer layer of extrusion. In US Pat. 5,599,383, the Dense layer is applied by chemical vapor deposition. To produce an even more complex architecture, several types Different treatment techniques can be applied. Is convenient, however, that the number of operations of treatment, be minimized because ceramic materials are Fragile by its very nature.

As will be examined, the present invention provides a cold isostatic compression method in which complex structures can be directly configured without the type of complex procedural steps that have been used in the prior art

Summary of the invention

The present invention provides a method of isostatic compression in which at least the first and second are compressed isostatically within a mold of isostatic compression so that at least the second layer is compacted and the first and second layers are stratified. The First and second layers can be configured of two materials different. The first layer could be of a granular material, for example of a metallic or ceramic powder that is compacted inside of the isostatic compression mold. The compacted element resulting could be coated with a mixture to form a second layer or the second layer could be another granular material that is compacted against the first layer. Other layers could be added or the compacted form could also be processed within A finished article. For example in the case of materials ceramic, the compacted form could be subjected to ignition to burn organic materials, such as binding agents and of plasticization, followed by sintering to produce the finished item. Alternatively, the first and second layers they can be formed with the same material, for example, if you want a thick ceramic article, the first layer that contains the material in the granular form could be compacted in a mold of cylindrical isostatic compression. After which, a second layer of the same material could be placed inside the mold of isostatic and compacted compression to start forming a thickness additional. One more possibility is to form at least one of the first or the second of the layers with at least two regions containing different materials It must be taken into account that the expression "granular form" as used herein and in the claims means a powder or a mixture of powders with other agents such as binding or plasticizing agents.

An isostatic compression mold that can be used to configure a tubular structure, such as the one required By a ceramic membrane element, it can be provided with a mandrel located coaxially inside the bearing element of cylindrical pressure to form a tubular structure. The first layer is formed around the mandrel and the second layer is formed Around the first layer. The resulting tubular structure it could be a tubular ceramic membrane element of the type previously described. In this regard, the two layers can be composed of untreated ceramic materials such as powders ceramic or ceramic powders mixed with other agents such as plasticizers, links and etc. or one of the two layers could be in the form of a ceramic that contains the mixture.

One way to form the first layer is set up a dry mix of coating on the mandrel that has been coated with a suitable release agent, containing the mix the first green ceramic material (recent). The second of the two layers can then be formed by compression isostatic of a second of the green ceramic materials (recent) in granular form against the dry mixture.

In order to form still more architectures complex, channel formation elements can be positioned  Between the layers Such channel formation elements can be configured of paper or other pyrolysable materials that burn during combustion to produce the channels between the layers.

Another alternative is to provide one or more of untreated ceramic materials in granular form with formers  of pores. Such pore formers, for example, can be starch, graphite, polyethylene beds, polystyrene beds, or saw dust. Therefore, a thin ceramic layer could be formed on the inside of a tubular membrane by, by example, a coating mixture on the mandrel. After what  which, the porous support layer could be formed by a untreated ceramic material containing the pore formers. After the ignition, the pore formers will burn to leave the pores In this regard, preferably pore formers  they are present inside untreated ceramic materials in sufficient quantities to produce a porosity of between about 1% and about 90% after burning.

As can be evident, additional layers that contain the same or different materials can be added to form a diversity porous or dense layers. Also at least one of the first and second layers can be formed from of at least two levels of different ceramic materials without try.

At least one of the ceramic materials without treat can be a mixed conductive oxide given by the formula:

A_ {x} A 'x' A '' x '' B_ {y} B 'y {} B_ {y' '} O_ {3-z},

where A, A ', A' 'are chosen from the groups 1, 2, 3 and the lanthanide block f; and B, B ', B' 'are chosen of block transition metals according to the Periodic Table of the Elements adopted by the IUPAC (International Chemistry Union Pure and Applied). In the formula 0 <x \ leq1, 0 \ leqx '\ leq1, 0 \ leqx '' \ leq1, 0 \ leqy \ leq1, 0 \ leqy '\ leq1, 0 \ leqy '' \ leq1 and z is a number that returns the composite load neutral Preferably, each of A, A ', and A' 'is magnesium, calcium, strontium or barium.

As an alternative, at least one of the untreated ceramic materials can be a conductive oxide mixed given by the formula: A 'S A' 't B_ u B' v B '' w O x where A represents a lanthanide, Y, or mixture thereof, A 'represents a metal alkaline earth or mixtures thereof; B represents Faith; B 'represents Cr, Ti, or mixtures thereof and B '' represents Mn, Co, V, Ni, Cu or A mixture of them. Each of s, t, u, v, and w represents a number from 0 to about 1. In addition, s / t is between around 0.01 and around 100, or is between about 0.01 and about 1, and x is a number that satisfies the valences of A, A ', B, B', and B '' in the formula. Further, 0.9 <(s + t) / (u + v + w) <1.1.

Brief description of the drawings

Although the description concludes with claims that distinctly indicate the subject that the Applicant considers how his invention believes that the invention is understand better when considered in relation to accompanying drawings, in which:

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Figure 1 is a schematic elevation view, sectional, of an isostatic compression mold that has a central mandrel in which loose powder is added to the mold of isostatic compression;

Figure 2 is a view of the compression mold isostatic of Figure 1 after the powder has been subjected to cold isostatic compression to reveal a separation or a annular space between the isostatic compression mold and the powder packaging;

Figure 3 illustrates the compression mold isostatic shown in Figure 2 after being added a second layer of dust loose to the annular space produced inside of the isostatic compression mold in the state shown in the Figure 2;

Figure 4 is a schematic illustration of the isostatic compression mold shown in Figure 3 after cold isostatic compression;

Figure 5 is a schematic illustration of an embodiment of the present invention in which the element of Cylindrical pressure support of isostatic compression mold of Figure 2 has been replaced with a load element of cylindrical pressure that has a different diameter to produce a composite structure that has layers of different thicknesses;

Figure 6 is a schematic illustration of an alternative embodiment to process the compression mold isostatic in the state shown in Figure 3 by adding of a channel of configuration material between the layers;

Figure 7 illustrates the compression mold isostatic in the state shown in Figure 6 after having underwent isostatic compression;

Figure 8 is a sectional illustration schematic of an isostatic compression mold of the type shown in Figure 1 after compaction and the addition of a second layer that has three different levels of material added.

Detailed description

Referring to Figure 1, an isostatic compression mold 2 is illustrated having a cylindrical pressure bearing element 30, base and end caps 32 34 and a mandrel 36 fixed to the base plug 32 to thereby produce a hollow tube. The first layer of material 38 could be of an untreated ceramic material in granular form or of a coating mixture on the mandrel 36. The untreated ceramic material in granular form may contain a porous forming material such as starch, graphite, beds of polyethylene, polystyrene beds, saw dust, and other known porous forming materials known. First and second layers 16 and 18 examined above with respect to the isostatic pressure mold 1 could also be provided with the formation material of
pores

With reference added to Figure 2, after isostatic compaction, end plug 34 can be disassembled and as shown in Figure 3, the mold 2 of hypostatic compression can be filled with a second layer of material 40, again possibly of a ceramic material without treat in granular form with or without the materials that form pores aligned above.

Alternatively, the support element 30 of the cylindrical pressure can be separated from the base plug 32 and the first compacted layer of material 38 could be coated by immersion with a mixture to form a second layer of material 40. Once dry, the isostatic compression mold 2 is reassembled to subject the second layer of material 40 to compaction isostatic It must be taken into account that the thickness of any layer formed by a mixture (either an inner or outer layer) It can be controlled by multiple solution applications of mixtures. Additionally, mixing solutions can they same contain pore formers. As such, multiple layers formed from mixtures can be produced having graduated porosities

As illustrated in Figure 4, a second layer of material 40 has been compacted by isostatic pressure to form a tube 42 of composite material. After which, the isostatic pressure mold 2 can be broken and tube 42 of composite material disassembled for subsequent processing such such as by heating or sintering or applying additional layers

With reference to Figure 5, as a alternative to the process shown in Figures 3 and 4, the plug 32 of  base can be disassembled from the pressure carrier element 30 cylindrical and a cylindrical pressure bearing element 44 of Small diameter can be substituted. A second layer of material 46 can be added then. The 2 'isostatic compression mold resulting is then sealed with an end cap 48. After isostatic compression, the second compacted layer of material 46 it must have a thickness less than that of the second compacted layer of material 40 shown in Figure 8. As can be seen process could be reversed using the first carrier element 44 of the cylindrical pressure and then a carrier element 30 of the cylindrical pressure so that the second layer is thicker than the first layer.

In the case where the article formed has to function as a ceramic membrane element, the materials ceramics used by the layers (for example, first and second layers 16 and 22 or first and second layers 38 and 40) can be a mixed conduction ceramic capable of conducting ions and electrons of oxygen Such materials could be in the form of powders or of powders mixed with other organic agents, in the case of a mixture, a typical composition could include about 120 grams of ceramic, 100 grams of a solvent such as toluene and 20 grams of organic binder, plasticizer, material coplastifier required to make a stable suspension.

Examples of such materials are set out in the table. next

one

2

3

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With additional reference to Figure 6, enter the time in which the second layer of material is added, such as a second layer of material 46 in Figure 5, a material 50 of Channel formation, in the form of strips, can be positioned between the first and second layers, 38 and 46. As illustrated in the Figure 7, after isostatic compression, material 50 of channel formation is located in front of the first and second of materials 38 and 46 for eventual withdrawal by combustion and other conventional techniques.

With reference to Figure 8, after being provided a first layer, such as that illustrated in Figure 1, and compacted, a second layer 52 can be added and compacted as shown in Figure 8. The second layer 52 can have three material regions 54, 56 and 58 to vary the type of material a along the length of the molded article. In practice, after compaction of the first layer as shown in the Figure 2, the powder that forms in region 58 is added to the mold at the desired level. After which the formation region 56 of powder is added to your desired level and the mold is completed with the dust that forms in region 54. Any and all of layers of material can be formed that way. How I know you can appreciate, are possible embodiments in which a layer with two regions or with four or more regions.

The cylindrical pressure bearing element 30 (or cylindrical pressure carrier element 44 for that reason) is preferably manufactures a material, which for the dimensions given of such elements, it will cause sufficient rigidity of the same so that ceramic materials can be introduced inside molds 1 and 2 of isostatic pressure while the cylindrical pressure bearing element 30 maintains its shape. To this  respect, the concern here is to prevent the wrinkling of cylindrical pressure bearing element 30 that could produce a hanging ceramic material inside the annular filled space formed between the cylindrical pressure bearing elements and their associated mandrels. In addition, that rigidity ensures that the section transverse transverse of that type of annular fill space remains constant along the length of the pressure mold isostatic so that the finished ceramic tube will be of a thickness constant. One more material consideration for the element of cylindrical pressure support used in this document is that the material must be elastic enough to contract or also eject out the pressure molded article isostatic to allow the untreated ceramic shape to end up being removal of the static pressure mold after the relaxation of Hydrostatic pressure

Preferably, the support elements of Cylindrical pressure are manufactured from materials such as the 95A hardness polyurethane on the durometric scale. Hardnesses between 75A and 75D on the durometric scale are also useful. Harder materials are preferred over more materials soft because it has been found that ceramic materials do not They tend to adhere to the hardest materials.

Claims (10)

1. A cold isostatic compression method that understands: cover a mandrel (36) of a mold (2) of isostatic compression with a first material; assemble a mold (2) of isostatic compression coaxially placing said mandrel within an element (30) of cylindrical pressure support and sealing said support element of cylindrical pressure at opposite ends, being one of said opposite ends of said pressure support element cylindrical sealed with an end cap (34) spaced from said mandrel; compressing said first material isostatically within said isostatic pressure mold to produce a first layer (38) in a form of a tube closed at one end and open at the other end of it; disassemble said isostatic pressure mold to allow said first layer to be covered with a second material; cover said first layer with said second material; reassemble said pressure mold isostatic; compressing said second material isostatically to form a compacted second layer (40) and to stratify the first and second layers; disassemble the mold and disassemble the structure tubular. 2. The method of claim 1, wherein the first and second materials comprise two materials different. 3. The method of claim 1, wherein the second material that forms the second layer (40) is a mixture. 4. The method of claim 1, wherein at least one of the first (38) and second (40) layers has the At least two regions that contain different materials. 5. The method of claim 1, wherein said at least two layers (38, 40) are composed of materials Ceramics without treatment. 6. The method of claim 5, wherein said first and second materials are in granular form. 7. The method of claim 5, in the that: the mandrel (36) is covered by said first material forming a dry mix coating on said mandrel, containing the dry coating of the mixture the first material; Y the second material is in a granular form before being compressed isostatically. 8. The method of claim 5, in the that: the first layer (38) is formed by entering the first material in a granular form inside the pressure mold isostatic and isostatically compressing said first material; Y the second layer (40) is formed by configuring a dry mixed coating on said first layer, containing The mixture coating dries the second material. 9. The method of claim 5, which it also includes positioning channel formation elements (50) on the first layer (38) before the formation of the second layer (40). 10. The method of claim 5, wherein at least one of the first and second materials before being tablets isostatically is in granular form and contains pore formers.